MainActivity.kt
package com.example.jetpack
import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import android.os.BatteryManager
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*
class MainActivity : AppCompatActivity() {
// initialize a new broadcast receiver instance
private val receiver:BroadcastReceiver = object: BroadcastReceiver(){
override fun onReceive(context: Context?, intent: Intent?) {
intent?.apply {
textView.text = "Current battery charge\n$currentBatteryCharge%"
}
}
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// initialize a new intent filter instance
val filter = IntentFilter(Intent.ACTION_BATTERY_CHANGED)
// register the broadcast receiver
registerReceiver(receiver,filter)
}
}
// extension property to get current battery charge percentage from intent
val Intent.currentBatteryCharge:Float
get() {
// integer containing the maximum battery level
val scale = getIntExtra(
BatteryManager.EXTRA_SCALE, -1
)
// integer field containing the current battery
// level, from 0 to EXTRA_SCALE
val level = getIntExtra(
BatteryManager.EXTRA_LEVEL, -1
)
// return current battery charge percentage
return level * 100 / scale.toFloat()
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/constraintLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#EDEAE0"
tools:context=".MainActivity">
<TextView
android:id="@+id/textView"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:fontFamily="sans-serif-condensed"
android:gravity="center"
android:padding="32dp"
android:textColor="#0014A8"
android:textSize="35sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.25"
tools:text="TextView" />
</androidx.constraintlayout.widget.ConstraintLayout>

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